The founder highly valued and favoured pure-blood students, and the sorting hat admitted that it can be a factor, but students of any blood status can now be placed in the house (however, a muggle born student is rare).

The emblematic animal of the house is a snake and its colours are green and silver. There were two notable heads of the house, Horace Slughorn took the role twice (first leaving in 1981 and then taking the role again from 1997 until leaving before 2016), and Severus Snape. The patron ghost of the house is the Bloody Baron.

Slytherin corresponds roughly with the element of water due to serpents being commonly associated with the sea and lochs in western European mythology, as well as serpents being physically fluid and flexible animals.[6] The colours also correspond with waters around lakes and lochs often being green, and silver being often associated with grey rain water.

Contents

Traits and values

Qualities

Slytherins tend to be ambitious, shrewd, cunning, strong leaders, and achievement-oriented. They also have highly developed senses of self-preservation.[7] This means that Slytherins tend to hesitate before acting, so as to weigh all possible outcomes before deciding exactly what should be done.

According to Albus Dumbledore, the qualities which Salazar valued in the students he chose included cleverness, resourcefulness, determination, and "a certain disregard for the rules." Dumbledore noted that all of these were qualities possessed by Harry Potter, who was in Gryffindor.

Another characteristic some Slytherins share is a tendency towards deep, unrequited love. According to legend, Merlin was said to hold a deep unrequited passion for the Lady of the Lake; and Severus Snape and The Bloody Baron held abiding but unreturned feelings for Lily Evans and Helena Ravenclaw, respectively. Although some Slytherins, such as Tom Riddle, were incapable of feeling love at all, those that did were known to cherish their passion abidingly and unconditionally, although often tragically due to an inability to act appropriately on their feelings.

Blood purity

"I always knew Salazar Slytherin was a twisted old loony, but I never knew he started all this pure-blood stuff. I wouldn't be in his house if you paid me. Honestly, if the Sorting Hat had tried to put me in Slytherin, I'd've got the train straight back home..."

The Sorting Hat claims that blood purity was a factor in selecting Slytherins. It is not the main factor but it suggests that the sorting hat takes in account the lineage of the student as well as traits. Muggle-born Slytherins exist, but are very rare, as noted insultingly by Scabior the Snatcher.[8]

The concept of blood purity playing a part in picking students for Slytherin house stems from the founder Salazar Slytherin who wanted a stricter policy of admission to the school — one limited strictly to pure-blood students. This was contrary to the wishes of the other founders at Hogwarts School of Witchcraft and Wizardry, who wanted to accept students of any blood status.

This created great controversy at Hogwarts and it was the root of a feud between former friends Salazar and Godric Gryffindor. Salazar would later decide to leave the school when an argument started between him and Godric and they either duelled or started a civil war between the two houses. It was the origin of the feud between their two houses who are the two most competitive of the houses.

When Salazar departed Hogwarts, he would leave behind the Chamber of Secrets with the purpose of an heir one day opening the chamber and unleashing a means of purging the school of any muggle-born students. The chamber was opened twice and the monster was killed the second time by Harry Potter in 1993. Salazar’s views at the time could be attributed to the persecution of witches and wizards at the hand of muggles in that century.

It is important to note that not every student in Slytherin agrees with the idea of blood purity, but every member would still be affiliated with their founder’s reputed views a thousand years later. Since the house would nearly always select students who share his view for that house, many members would still give that impression of that house during their time at Hogwarts. For example, in December 1992, the password for the common room was pureblood.

Slytherin and Gryffindor are generally rivals in Quidditch and for the House Cup, which the former had won seven years in a row prior to Harry Potter's arrival at Hogwarts in 1991. It is also rare for Slytherin and Gryffindor students to be friendly with one another, and common for them to share animosity. There are exceptions, such as Slytherin Severus Snape and Gryffindor Lily Evans, who were best friends until Snape's use of the slur "Mudblood" and his aspirations to be a Death Eater which caused Lily to sever their ties.

Their rivalry was particularly the case during the First and Second Wizarding Wars. During the second war, no Slytherin student joined the association known as Dumbledore's Army; however, this is likely the fault of Hermione Granger, Ron Weasley, and Harry Potter who only invited people they trusted. The three shared a deep mistrust of any Slytherins.

The behaviour of Slytherin house at the Battle of Hogwarts is also debated. The majority of their members departed Hogwarts before the battle started and a few joined their families in becoming Death Eaters. However, many of them returned to Hogwarts to fight against the Death Eaters and were led back by their Head of House, Horace Slughorn.

Reputation

"There's not a single witch or wizard who went bad who wasn't in Slytherin."

Slytherin has a such well-known reputation for creating dark witches and wizards that many would even say that every dark witch or wizard was actually in Slytherin. While it is true that many were in the house, it is untrue to say every single one of them was, as Peter Pettigrew was in Gryffindor and Quirinus Quirrell was in Ravenclaw for example.

It appears that reputation has led to an ironic prejudice against the entire house. It is unknown how many dark witches and wizards were from this house before Tom Riddle began recruiting Death Eaters but many of them came from a family that valued blood purity and would prefer like Tom, to be in the house and recruit from there.

It might also be possible (though quite unlikely) that the Sorting Hat simply sorts anyone with ill intentions into Slytherin, regardless of whether they possess cunning and ambition, which helped to unfairly give this house a bad name. Vincent Crabbe and Gregory Goyle were both incredibly stupid and did not have clever or cunning minds, but were still sorted into Slytherin. They could have possessed one of the minor traits as even Peter Pettigrew was not placed into Gryffindor for bravery, but by chivalry instead.

It is also likely that Crabbe and Goyle were simply placed there by process of elimination, since they exhibited virtually none of the qualities valued by any of the other houses (lacking the work ethic or honesty of Hufflepuff, the academic prowess of Ravenclaw, or the bravery of Gryffindor). The sorting hat simply could have took into account what house they wished to be placed in, which with their family history was most likely Slytherin.

House ghost, The Bloody Baron

The traits of the house are considered obvious examples of people turning toward an ill purpose such as cunning and ambition but they are not inherently negative. Furthermore, traits from the rest of the houses such daring, intelligence, and loyalty can also become easily negative.

Another trait which is could be such a negative is self-preservation. The idea that many of them seem to value their own lives more than the lives of others can make them less thought of and trusted, but that is not always the case. Phineas Nigellus gave that impression when he saw Harry Potter trying to run away, because he was afraid that his presence was putting his friends in danger. He stated that "We Slytherins are brave, yes, but not stupid. For instance, when given the choice, we will always choose to save our own necks".

There are exceptions to this rule, however, such as Snape, who Harry said was a "Slytherin and... probably the bravest man I ever knew", and Regulus Black, who gave his life in an attempt to destroy one of the Horcruxes of Lord Voldemort and told his house-elf Kreacher to save himself and leave.

The truth is that while most Dark wizards are Slytherins, many members of Slytherin House do not have Dark leanings and are even kind and accepting, while smaller groups of Voldemort's supporters are aligned with other Houses. During the Battle of Hogwarts, while all of the Slytherin students left the school before the fighting started, several of them did return with Professor Slughorn as reinforcements to join the fight against Lord Voldemort and his Death Eaters, and some decided to fight as a part of Dumbledore’s Army.

Common Room

The Slytherin common room is in the dungeons of Hogwarts Castle and underneath the Black Lake. Because of this, the light in the common room is green. Harry Potter along with Ron Weasley entered the common room in his second year to find out if Draco Malfoy was the one opening the Chamber of Secrets. To enter the Slytherin common room one must merely speak aloud the current password in front of a stretch of damp stone wall; once the word is uttered a concealed stone door will slide aside leaving a rectangular hole in the wall leading to the Slytherin common room. The only known Slytherin password is "pureblood", used in 1992.

Known Slytherins

Hot-tempered lord and squire who remorsefully committed suicide for inavertentally killing his unrequited lover in a fit of rage when she refused to come home from Albania with him, leaving his clothes stained with her blood. Later became the house ghost.

Klastūnynas (taken from the noun 'klasta' meaning 'guile' or 'ruse'. Also could be translated as 'viper' or 'scoundrel'.)

The same name is used for the Arabic, Croatian, German, Hebrew, Swedish, Spanish, Danish, Turkish, Icelandic, Irish, Polish, Portuguese (Portugal), and Indonesia languages.

Slytherin

Behind the scenes

Slytherin Banner

The fact that J. K. Rowling intended to place a character named Mafalda, a half-blood who was the daughter of a Squib and a Muggle, in Slytherin, suggests that Rowling at least does not view the Slytherin House desire for blood-purity as particularly influential upon the Sorting Hat. Also as Voldemort and Snape are both half-bloods there seems no reason to suspect a racially pure Slytherin.[13]